Availability Guide for Application Design

Availability in the Pathway Transaction-Processing
Environment
Availability Guide for Application Design—525637-004
6-4
NonStop TS/MP and Highly Available Server
Processes
NonStop TS/MP and Highly Available Server
Processes
NonStop TS/MP supports server processes through monitoring, load balancing, and
providing linkage with requesters. Figure 6-2 on page 6-5 shows the major
components of NonStop TS/MP and the requesters for which they secure services.
What Is NonStop TS/MP?
The major components of NonStop TS/MP are PATHMON and LINKMON.
In H-series systems, the link manager functions are not provided by LINKMON (a
process), but by the Application Cluster Services (ACS) subsystem. (At the level of
detail supplied in this manual, the concepts are really interchangeable as ACS is a low-
level subsystem not configured by most users.)
The PATHMON process provides:
•
Automated monitoring of Pathway objects including servers, terminal control
processes (TCPs), and terminals
A TCP is a requester process supplied by HP as part of the Pathway/iTS product.
It provides an environment for interpreting user-written requester programs for
supported terminals.
•
Control of the number of instances of a server process in a given server class to
ensure that enough servers are available to handle the workload
•
A user interface (PATHCOM) that allows operator control of the functions of the
PATHMON process. Refer to Availability Through Pathway/iTS on page 6-24 for a
discussion of the TCP and requester programs.
The link manager function (LINKMON or ACS) works with the PATHMON process to
provide linkage with Pathsend requester processes. Refer to Availability Through
Pathsend on page 6-18 for more information about the link manager function.
Availability of NonStop TS/MP Server Processes
The Pathway transaction-processing environment is designed to use process
replication as the means for keeping services available. Other approaches can work,
such as running the server process as a process pair or saving context on disk.
However, this discussion focuses on process replication.
A group of replicated server processes is known as a server class.
When Is Recovery Action Needed?
The system or application needs to take recovery action if a server process stops. A
server process might stop for any of the following reasons: